Articles in press have been peer-reviewed and accepted, which are not yet assigned to volumes /issues, but are citable by Digital Object Identifier (DOI).
Display Method:
MORE
2021, Volume 42, Issue 9 publish date:September 01 2021
Display Method:
Fluid Mechanics
Machine Learning With Physical Empirical Model Constraints for Prediction of Shale Oil Production
ZHOU Jimin, ZHANG Haichen, WANG Moran
2021, 42(9): 881-890.   doi: 10.21656/1000-0887.420015
Abstract(44) PDF(9)
Abstract:
Prediction of oil and gas production is an important way to determine its development economy. However, at present the production prediction is still hard to achieve consistency between the physics-based method and the data-based method. For shale oil and gas production analysis, in-depth combination of mathematical advantages brought by BP neural networks and LSTM neural networks, and comprehensive consideration of physics-based models, lead to good improvement in the prediction accuracy of the model. After training with practical testing data, the prediction of oilfield production can be significantly improved. Afterwards, the effects of the reservoir depth, the TOC and the brittleness, etc. on production prediction were studied. In conclusion, the work provides reliable production prediction and economic evaluation for large-scale development of shale oil and gas.
A Low-Order Model Method for 2-Phase Oil Reservoir Simulation
JIA Xinxin, WANG Lei, ZHANG Hao, SUN Xiaoling, DUAN Liya, WANG Xin
2021, 42(9): 891-899.   doi: 10.21656/1000-0887.410235
Abstract(41) PDF(2)
Abstract:
At present, the main methods used in reservoir numerical simulation, such as the finite element method and the finite volume method, require long calculation times, which limit their implementation in the real-time prediction and the reservoir production. An efficient data-processing method that based on the POD (proper orthogonal decomposition) was proposed to obtain the empirical coefficients and eigenfunctions of the oil-water 2-phase flow in the reservoir, and build a new low-order Galerkin calculation model. The numerical calculation indicates that, with the POD, the calculated eigenvector energy has proper features. Only a small number of eigenvalues can capture most of the energy, completely describe the reservoir characteristics (pressure, saturation), and help reduce the order of the partial differential equations. The calculation results of the low-order model are in good agreement with those from the IMPES, with much time saved. The proposed method applies well to history matching in numerical simulation of reservoir injection and production.
An Investigation on the Immiscible Displacement in Porous Media With Contact Angle Hysteresis
CHEN Jiahao, LOU Qin
2021, 42(9): 900-914.   doi: 10.21656/1000-0887.410278
Abstract(32) PDF(1)
Abstract:
Contact angle hysteresis is the difference between advancing and receding contact angles, and makes an important phenomenon in 2-phase flow on a wetting surface. An improved interparticle potential model was coupled with the geometrical formulation contact angle scheme to investigate the effects of the contact angle hysteresis, the capillary number, and the geometry structure on immiscible displacement issues in porous media. The numerical results show that, the displacement efficiency increases with the receding angle for a given capillary number and a given advancing angle. On the other hand, for 3 types of contact angle hysteresis windows: hydrophilic, neutral and neutral hysteresis windows, the displacement efficiency of hydrophilic hysteresis windows is higher than that of neutral and hydrophobic conditions. Furthermore, in hydrophobic and neutral contact angle hysteresis windows, the displacement efficiency decreases with the hysteresis window magnitude. In the same contact angle hysteresis for single-permeability porous media, a larger Ca number makes the viscous fingers more obviously, so the displacement efficiency decreases with the capillary number. For the dual-permeability porous media, it is easier for the displacing phase flows to finger in high-permeability areas and break through the boundary first. As a result, in the high-permeability area the displacement efficiency is significantly higher than that in the single-permeability area. The heterogeneity of dual-permeability porous media will enhance the influence of contact angle hysteresis on the distribution of the displacing or displaced fluid, but limit the influence on the displacement efficiency.
A “Standard Cross-Section” Method for the Calculation of Riverbed and Bank Shear Stresses
LUO You, ZHU Senlin, CAO Bing, JIANG Chenjuan
2021, 42(9): 915-923.   doi: 10.21656/1000-0887.420048
Abstract(41) PDF(3)
Abstract:
Seeking for the “zero shear stress dividing line” and quantifying the apparent shear stress at the interface between adjacent sub-regions are 2 main methods to calculate the riverbed and bank shear stresses. To simplify the empirical expression for apparent shear stresses along the dividing line, a “momentum transfer-equilibrium deviation” (MTED) assumption that the apparent shear stress can be calculated based on the deviation of momentum transportation from its equilibrium value, was proposed. A “standard cross-section” concept was applied to determine the equilibrium value. All the rectangular and trapezoidal cross-sections can be correlated with certain standard cross-sections. Based on the MTED assumption and the concept of standard cross-sections, the empirical expressions for the apparent shear stresses along the dividing line and the bed and bank boundary shear stresses, were established. More than 200 data from different lab experiments were used to verify different methods. The results show that, the proposed method improves the calculation accuracy and can be applied to both rectangular and trapezoidal cross-sections, as well as to both smooth and rough channels.
Existence and Blowup of Positive Solutions to a Class of Multilateral Flow Equations
LI Jianjun, TANG Yina
2021, 42(9): 924-931.   doi: 10.21656/1000-0887.420022
Abstract(31) PDF(1)
Abstract:
The global existence and blowup of the solutions to a class of multilateral filtration equations with non-local Neumann boundary conditions and nonlinear absorption terms were studied. First, the super- and sub-solutions were defined for the studied equations and the comparison principle was established. Then, the equation was investigated with constructed functions, differential inequalities, eigenfunctions, ordinary differential equation and elliptic second boundary value solutions. The global existence of non-negative solutions to the equations and the conditions for blowup in a finite time for the parameters, weight functions and initial values in different value ranges were obtained.
Applied Mathematics
Study on Numerical Solutions to Hyperbolic Partial Differential Equations Based on the Convolutional Neural Network Model
GAO Puyang, ZHAO Zitong, YANG Yang
2021, 42(9): 932-947.   doi: 10.21656/1000-0887.420050
Abstract(42) PDF(9)
Abstract:
In recent years, artificial neural networks developed rapidly. Application of this method to partial differential equations became a new idea for exploring numerical solutions to differential equations. Compared with the traditional methods, it has some advantages, such as a wide range of applications (i.e. the same model can be used to solve multiple types of equations) and low meshing requirements. In addition, the trained model can be directly used to calculate the numerical solution at any point in the computation domain. The weight coefficients in the traditional finite volume method were optimized based on the convolutional neural network model to get a new numerical scheme with highresolution results on the coarse grid. The proposed model helps solve the Burgers and level set equations efficiently and stably with high accuracy.
Singularly Perturbed and Soliton Solutions to a Class of KdV-Burgers Equations
BAO Liping, LI Ruixiang, WU Liqun
2021, 42(9): 948-957.   doi: 10.21656/1000-0887.420011
Abstract(47) PDF(3)
Abstract:
A class of KdV-Burgers equations with large Reynolds numbers and weak dispersions were discussed, which were mathematically expressed as a class of singularly perturbed KdV-Burgers equations. The interaction between the nonlinear term and the dispersion term in the KdV-Burgers equation forms a stable forward-propagation soliton. Through mathematical analysis, the propagation path and speed of the soliton were described. By means of the singularly perturbed expansion method, the asymptotic solution to the problem was constructed. First, the degenerate solution was obtained with the Riemann-Earnshaw method, and the simple wave was obtained. There is a velocity difference between any point of the simple wave shape and the initial point, which makes the wave form continuously distorted in the process of propagation, and finally forms the shock wave surface, namely discontinuity. There is a time-varying jump in the velocity of particles between both sides of the discontinuity. Second, a modified traveling wave transformation was built through substitution of variables at the discontinuity of the degenerate solution, to obtain soliton solutions of the expansion of internal solutions and prove the existence and uniqueness of the internal and external solutions. Finally, the residual term was estimated with the existence of the uniformly bounded inverse operator, and the uniform effectiveness of the asymptotic solution was obtained. The results show that, the perturbations of KdV-Burgers equations with large Reynolds numbers and weak dispersions concentrate on the neighbourhoods of the discontinuities of the degenerate solutions. The soliton links the particles across the 2 sides, and its propagation path is not a linear form of time and space, but leads along the discontinuity of the degenerate solution, forming a stable waveform.
Stability of Vector Optimization Problems Under Approximate Equilibrium Constraints via Free-Disposal Sets
ZENG Yue, PENG Zaiyun, LIANG Renli, SHAO Chongyang
2021, 42(9): 958-967.   doi: 10.21656/1000-0887.410244
Abstract(46) PDF(5)
Abstract:
The stability of vector optimization problems under approximate equilibrium constraints (AOPVF) via free-disposal sets was discussed. Firstly, the Berge-semicontinuity of the constraint set mapping and the closedness, the convexity and the compactness of the constraint set were obtained with the weaker convexity assumption. Moreover, under the assumption of Gamma-convergence for the objective functional sequences, the lower Painlevé-Kuratowski convergence of the weak efficient solution set and the Berge-semicontinuity of weak efficient solution mappings for AOPVF were obtained respectively. Some examples illustrate that the results are new and meaningful.
The Phragmén-Lindelöf Type Alternative Results for Binary Heat Conduction Equations
LI Yuanfei, ZENG Peng, CHEN Xuejiao
2021, 42(9): 968-978.   doi: 10.21656/1000-0887.420031
Abstract(36) PDF(4)
Abstract:
The asymptotic behavior of the solution to the binary heat conduction equation in the semi-infinite domain was considered, in which the local non-homogeneous Neumann condition was applied to the side of the cylinder. This condition simulates the local damage of the insulation material on the side of the cylinder. By means of the differential inequality technique and the energy analysis method, the Phragmén-Lindelöf-type alternative results of the heat conduction model were obtained.
The Random ADMM and Its Application to Convex Economic Dispatch Problems of Power Systems
CHEN Weijun, LUO Honglin, PENG Jianwen
2021, 42(9): 979-988.   doi: 10.21656/1000-0887.420040
Abstract(38) PDF(3)
Abstract:
A new random alternating direction method of multipliers (ADMM) was designed to solve convex economic dispatch problems in power systems. The convergence of the random ADMM was analyzed. Under some mild assumptions, the random ADMM, according to the cycle update rule and the random selection update rule, was proved to converge to an optimal solution of the convex economic dispatch problem. The numerical experimental results show that, the proposed method is effective to solve convex economic dispatch problems.
Block-Sparse Signal Recovery via l2/lq(q=2/3) Minimization
ZHU Dechun, ZHOU Jun, CAO Manxia, HUANG Wei
2021, 42(9): 989-998.   doi: 10.21656/1000-0887.420009
Abstract(44) PDF(2)
Abstract:

The recovery of block-sparse signals was mainly studied. By means of the block restricted q-isometry property (block q-RIP) with 0<q≤1, a sufficient condition for block-sparse signal recovery was established through mixed l2/lq(q=2/3) norm minimization with q=2/3,and an error bound for signal recovery in the presence of noise was obtained. Through numerical experiments, it is verified that the model has a high success rate for block-sparse signal recovery.

Damage Identification for Bridge Structures Based on the Wavelet Neural Network Method
XIAO Shu-min, YAN Yun-ju, JIANG Bo-lan
2016, 37(2): 149-159.   doi: 10.3879/j.issn.1000-0887.2016.02.004
[Abstract](800) [PDF 5386KB](724)
摘要:
桥梁结构在服役期间会承受复杂的荷载,长期使用会不可避免地出现各种损伤。若这些损伤不能被及时发现和适当处理,将有可能造成严重的事故。因此,桥梁结构的局部小损伤识别对于其及时检修有重要意义。通常,损伤结构的全局动态特性测试可能对局部的结构损伤不敏感,特别是对小损伤,这就需要从结构动态响应信号中提取对损伤更敏感的特征量。建立了桥梁结构的有限元模型并进行动力特性分析;采用小波包分析方法处理结构动态响应信号以构造结构损伤指标,并结合结构损伤指标和人工神经网络方法进行桥梁结构的损伤定位.
The PseudoExcitation Method and Its Industrial Applications in China and Abroad
LIN Jia-hao, ZHANG Ya-hui, ZHAO Yan
2017, 38(1): 1-31.   doi: 10.21656/1000-0887.370578
[Abstract](926) [PDF 1039KB](1409)
摘要:
《随机振动的虚拟激励法》自1985年正式发表以来,逐渐得到许多工程领域的认可和采用,解决了很多重要而困难的工程问题.该方法不但被国内某些工程规范所推荐,而且被3种国际工程手册成章刊载,在国际上亦占有了一席之地.该文是笔者参考了数百篇国内外论文,依据其中一部分在11个工程领域对虚拟激励法的应用和一些学者的评论所撰写的综述.借以让更多工程技术人员和研究者对虚拟激励法有较为全面的了解,以结合各自工程领域更有效地开展对随机振动理论和方法研究成果的应用和发展.
Uncertainty Quantification for System Identification Utilizing the Bayesian Theory and Its Recent Advances
YAN Wang-ji, CAO Shi-ze, REN Wei-xin.
2017, 38(1): 44-59.   doi: 10.21656/1000-0887.370571
[Abstract](746) [PDF 647KB](918)
摘要:
受测试误差、建模误差、数值离散化以及环境变异等因素的影响,结构系统识别过程不可避免地存在不确定性,因此有必要引入概率统计方法来提高其鲁棒性,为工程结构安全监测提供更为可靠的结果.近年来,Bayes(贝叶斯)方法因为其诸多优势在系统识别领域受到了广泛关注.该文梳理了Bayes系统识别的历史脉络和研究进展.从Bayes系统识别的理论框架出发,分析了量化系统识别不确定性两类方法的适用条件与局限性.此外,文章综述了Bayes方法在模态参数识别、有限元模型修正以及结构损伤识别方面进行不确定性分析的理论、实现及其应用.最后对基于Bayes方法进行系统识别研究的发展趋势做出了展望.
Detached-Eddy Simulation of Flow Past Tandem Cylinders
ZHAO Wei-wen, WAN De-cheng
2016, 37(12): 1272-1281.   doi: 10.21656/1000-0887.370546
[Abstract](535) [PDF 3862KB](607)
摘要:
主要开发了SST-DES和SST-DDES两种分离涡方法,并集成到基于开源代码平台OpenFOAM开发的CFD求解器naoe-FOAM-SJTU中.选用高Reynolds(雷诺)数下串列双圆柱绕流问题作为标准算例来验证所开发的分离涡方法.该标准算例此前在美国国家航空航天局兰利研究中心的两个不同风洞做过物理试验.该研究将数值模拟得到的时均流场信息和一些其他物理量同物理试验结果比较,同时讨论分析了三维瞬态流场结构.结果表明该文开发的SST-DES和SST-DDES分离涡方法能够解决高Reynolds数下有大量流动分离的复杂流动问题.
Convergence Results on Heat Source for 2D Viscous Primitive Equations of Ocean Dynamics
LI Yuanfei
2020, 41(3): 339-352.   doi: 10.21656/1000-0887.400176
[Abstract](391) [FullText HTML](26) [PDF 405KB](285)
摘要:
考虑了在一个柱形区域上的海洋动力学中二维黏性方程组解的收敛性.在此模型中存在一个关键的参数就是热源,众多周知,它的存在可能会使流体内层之间出现共振从而导致不稳定.因此,通过推导方程组的先验界,得到了方程组的解对热源自身的收敛性.
Simulation of Multi-Hydrofracture Horizontal Wells in Shale Based on the Extended Finite Element Method
CHEN Jun-bin, WEI Bo, XIE Qing, WANG Han-qing, LI Tao-tao, WANG Hao
2016, 37(1): 73-83.   doi: 10.3879/j.issn.1000-0887.2016.01.006
[Abstract](792) [PDF 1871KB](678)
摘要:
页岩储层水平井分段多簇压裂簇间距优选是压裂技术的关键,建立了水力压裂流固耦合数学模型,基于扩展有限单元法模拟多条裂缝的扩展过程,研究多条裂缝同时扩展的转向规律,以及应力干扰、水平主应力差、裂缝间距等因素与裂缝转向角度的关系.结果表明:应力干扰作用对裂缝宽度具有限制作用,单条裂缝张开宽度比两条裂缝的大;裂缝转角随应力差的减小而增大,随压裂时间的增加而增大.簇间距越小,应力干扰越强,转角越大,综合主缝均匀扩展、支撑剂填充以及复杂裂缝网络形成等条件,确定最优簇间距为30~40 m.多条裂缝同时扩展时,中间裂缝会受到两边裂缝的限制作用,簇间距越小,限制作用越强,裂缝发育时间越长,扩展速度越慢.
Analysis on Shear Deformation and Shear-lag Effects on Twin-Cell Box Girders
ZHANG Hui, ZHANG Yu-yuan, ZHANG Yuan-hai, LI Wei
2016, 37(8): 791-803.   doi: 10.21656/1000-0887.370056
[Abstract](641) [PDF 589KB](822)
摘要:
基于各个翼板选取不同的最大剪切转角差为剪力滞广义位移,应用能量变分原理分别推导出了考虑和不考虑剪切变形时单箱双室截面控制微分方程组,结合边界条件给出了箱梁纵向应力和竖向挠度的初参数解,从力学、数学角度上证实了剪切变形和剪力滞效应是两个相对独立的力学行为,进一步阐述了二者对箱梁的影响,即剪切变形对箱梁截面纵向应力无影响,但是对竖向挠度有很大的影响.数值算例表明,利用该文解和数值解分析跨中截面剪力滞系数横向分布规律,二者吻合程度良好,其横向分布规律与单室箱梁类似,唯独不同之处是边腹板处的剪力滞效应比中腹板处的剪力滞效应略微大一些;挠度计算表明,剪切效应使得该箱梁在集中和均布荷载作用下跨中挠度分别增大4.6%和2.7%.
Some New Advances in the Probability Density Evolution Method
LI Jie, CHEN Jian-bing
2017, 38(1): 32-43.   doi: 10.21656/1000-0887.370336
[Abstract](690) [PDF 683KB](2030)
摘要:
介绍了随机动力系统中概率密度演化理论的基本方程与求解方法〖CX4〗.〖CX〗在此基础上,论述了广义概率密度演化方程求解的若干新进展,包括群演化方程及其求解、概率空间剖分的理性准则、点集加密技术与信息拓展方法等.
Investigations of Self-Propulsion in Waves of Fully Appended ONR Tumblehome Model
WANG Jian-hua, WAN De-cheng
2016, 37(12): 1345-1358.   doi: 10.21656/1000-0887.370525
[Abstract](720) [PDF 3993KB](543)
摘要:
采用基于重叠网格技术的CFD方法数值研究了全附体ONRT船模在迎浪工况中自航的水动力特性.文中数值计算采用自主开发的面向船舶与海洋工程的CFD求解器naoe-FOAM-SJTU.自航计算中船体运动及螺旋桨转动等通过重叠网格技术完成,波浪环境则采用求解器中的三维数值造波和消波模块实现.计算中自航船模的螺旋桨转速通过静水自航数值计算得出,波浪工况计算采用东京2015 CFD会议中标准算例进行设置.数值计算结果,如船体运动、实时航速变化等,与试验数据进行了对比分析.此外,给出了数值预报的推力和扭矩系数,并且通过详细的流场信息来分析和解释了船模在波浪中自航过程中的水动力变化情况.数值预报结果同试验值吻合较好,说明采用当前结合重叠网格技术和CFD的数值方法可以很好地预报波浪中自航问题.
Chaos Control for the Duopoly Cournot-Puu Model
DU Lin, ZHANG Ying, HU Gao-ge, LEI You-ming
2017, 38(2): 224-232.   doi: 10.21656/1000-0887.370256
[Abstract](591) [PDF 890KB](503)
摘要:
基于非线性动力学的基本原理,研究了经济系统中的双寡头垄断Cournot-Puu模型及其混沌控制方法.Cournot-Puu模型具有双曲线形需求函数和彼此不同的不变边际成本,离散化的差分系统显示出其复杂的非线性、分岔和混沌行为.在此基础上,结合Cournot-Puu模型的基本特征,应用延迟反馈控制方法以及自适应控制方法对该系统的混沌行为进行了研究.在结合实际经济意义的条件下,对该模型的输出进行调整并实现混沌控制.
Study of Stress Field Near Interface Crack Tip of Double Dissimilar Orthotropic Composite Materials
LI Jun-lin, ZHANG Shao-qin, YANG Wei-yang
2008, 29(8): 947-953.  
[Abstract](2804) [PDF 460KB](9)
Abstract:
A study of double dissintilar orthotropic composite materials interfacial crack was made by constivcting new stress functions and employing the method of composite material complex.In the case that the characteristic equations' discriminants are all more than zero,the theoretical fonmula of the stress field and the displacement field near the mode Ⅰ interface crack tip,without oscillation and inter-embedding between the interfaces of the crack were delved.
Second Order Approximation Solution of Nonlinear Large Deflection Problem of Yongjiang Railway Bridge in Ningbo
CHIEN Wei-zang
2002, 23(5): 441-451.  
[Abstract](4865) [PDF 395KB](45)
Abstract:
The solution and computational aspects on nonlinear deflection of Yongjiang Railway Bridge in Ningbo were investigated.An approximate iteration algorithm on nonlinear governing equation was presented,and the obtained results show that,if altitude difference and span of the riverbanks are taken as 5 meters and 100 meters,respectively,the maximum gradient in the middle of the bridge exceeds 5%,much larger than maximum allowance gradient in railway design code.Therefor,a new solution scheme for decreasing gradient of the bridge is put forward,that is,the altitude difference between two riverbanks can be decreased to about 1/10 of the initial magnitude by building roadbeds with 0.5% gradient and 1 kilometer length at two riverbanks.As a direct result,the deflection gradient of the railway bridge is much reduced and the value is between 0.5%~0.6%.